JP3682120B2 - Composite membrane for battery separator and battery separator - Google Patents
Composite membrane for battery separator and battery separator Download PDFInfo
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- JP3682120B2 JP3682120B2 JP16377696A JP16377696A JP3682120B2 JP 3682120 B2 JP3682120 B2 JP 3682120B2 JP 16377696 A JP16377696 A JP 16377696A JP 16377696 A JP16377696 A JP 16377696A JP 3682120 B2 JP3682120 B2 JP 3682120B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E60/10—Energy storage using batteries
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Description
【０００１】
【発明の属する技術分野】
本発明は、リチウム電池等の非水溶媒電池に対応するセパレーターとして使用される、透過性能及び機械的強度に優れるとともに、短絡による異常発熱時において低温で透過性を遮断する機能を有し、かつ安全性の高い電池セパレーター用複合膜に関するものである。
【０００２】
【従来の技術】
ポリオレフィン微多孔膜は、各種の分離膜や、電池用セパレーター、電解コンデンサー用セパレーター等に使用されている。特にリチウム電池においては、リチウム金属、リチウムイオンが用いられているために非プロトン性極性有機溶媒が電解液溶媒として用いられ、また、電解質としては、リチウム塩を用いている。したがって正極と負極との間に設置するセパレーターには、有機溶媒に不溶でありかつ電解質や電極活物質に対して安定なポリエチレン、ポリプロピレンなどのポリオレフィン系材料を微多孔膜や不織布に加工したものをセパレーターとして用いている。
【０００３】
最近、超高分子量のポリオレフィンを用いて高強度および高弾性の微多孔膜が開発されてきている。例えば、重量平均分子量が７×１０5 以上の超高分子量ポリオレフィンを溶媒中で加熱溶解した溶液からゲル状シートを成形し、前記ゲル状シート中の溶媒量を脱溶媒処理により調整し、次いで加熱延伸した後、残留溶媒を除去することにより、微多孔膜を製造する方法が提案されている（特開昭６０−２４２０３５号他）。また、超高分子量ポリオレフィンの高濃度溶液からのポリオレフィン微多孔膜の製法として、超高分子量ポリオレフィンを含有するポリオレフィン組成物の分子量分布を特定の値にする方法が提案されている（特開平３−６４３３４号）。
【０００４】
ところで、上記ポリオレフィン微多孔膜をリチウム電池用セパレーター等に用いる場合には、電極が短絡して電池内部の温度が上昇した時に、発火等の事故が生じるのを防止する必要がある。このため、リチウムの発火以前に溶融してその孔を目詰りさせ、電流をシャットダウンさせる機能をセパレーターに持たせる必要がある。ところが上記各微多孔膜においては微多孔膜の閉塞による透過性遮断温度が安全性の点で必ずしも十分に低いものではなく、より一層安全性を向上させるためには、さらに低い温度で電流のシャットダウンを起こすセパレーターとすることが望ましい。したがって、低い無孔化温度を有しているほど、かつ、無孔化温度と膜破れ温度の差が大きいほど、高温特性が良好で安全性の高い電池用セパレーターになりうると考えられる。
【０００５】
電池用セパレーターの短絡時のシャットダウン機能を付与する技術としては、特開昭６０−２３９５４号公報に、電池が外部ショートした場合にジュール熱により電池内温度が上昇してセパレーター部材が溶融し、内部ショートして電池の発火、爆発等の事故防止をする目的で、ポリプロピレンまたはポリエチレン製の単層の微孔性フィルムを使用することが望ましいと開示されている。
【０００６】
ポリプロピレン及びポリエチレン製微孔性フィルムを用いた電池では、外部ショートさせた場合、ジュール熱で電池温度が上昇して各フィルム素材の有する溶融点に達すると微細孔が溶融物で塞がれ、電気的絶縁は勿論のことイオンの移動も阻止する絶縁体となるため電流は流れなくなる。その結果、電池温度もそれ以上に上昇することなく発火や爆発といった不都合は抑制されることになると記載されている。しかしながら、上記の非水電解液型セパレーターでは、ある程度安全性は向上するものの、温度が上昇し、熱可塑性樹脂の融点近傍では樹脂の凝集力が小さくなってしまい、セパレーターが破れてしまう場合があり、発火、爆発の危険性の解決には十分とはいえない。
【０００７】
【発明が解決しようとする課題】
したがって、本発明の課題は、透過性能及び機械的強度に優れるとともに、低温で透過性を遮断する機能を有する安全性に優れた電池セパレーター用複合膜を提供することである。
【０００８】
【課題を解決するための手段】
本発明は、上記課題を達成するため、超高分子量ポリオレフィンまたはその成分を含有する組成物からなる微多孔膜とポリプロピレン製不織布を積層することにより、透過性能及び機械的強度に優れるとともに、低温で透過性を遮断しかつ安全性に優れた複合膜が得られることを見いだし、本発明に想到した。
【０００９】
すなわち、本発明の第一は、重量平均分子量が５×１０5 以上のポリオレフィンまたは重量平均分子量が５×１０ 5 以上の超高分子量ポリオレフィンを含有するポリオレフィン組成物からなり、空孔率が３０〜９５％、平均貫通孔径が０．００１〜１μｍ、引張り破断強度が５００ｋｇ／ｃｍ2 以上であるポリオレフィン微多孔膜に、ポリプロピレン製不織布を積層した電池セパレーター用複合膜に関するものである。
【００１０】
また、本発明の第二は、重量平均分子量５×１０5 以上のポリオレフィンを含有するポリオレフィン組成物が、（ａ）重量平均分子量１×１０6 〜１５×１０6 の超高分子量ポリオレフィンまたは（ａ）重量平均分子量１×１０6 〜１５×１０6 の超高分子量ポリオレフィンと（ｂ）重量平均分子量１×１０5 以上１×１０6 未満のポリオレフィンとの組成物７０〜９５重量％と、（ｃ）重量平均分子量が１０００〜４０００で、融点が８０〜１３０℃の低分子量ポリエチレン５〜３０重量％とからなり、空孔率が３０〜９５％、平均貫通孔径が０．００１〜１μｍ、引張り破断強度が５００ｋｇ／ｃｍ2 以上であるポリオレフィン微多孔膜に、ポリプロピレン製不織布を積層した電池セパレーター用複合膜に関するものである。
【００１１】
さらに、本発明の第三は、重量平均分子量５×１０5 以上のポリオレフィンを含有するポリオレフィン組成物が、（ａ）重量平均分子量１×１０6 〜１５×１０6 の超高分子量ポリオレフィンまたは（ａ）重量平均分子量１×１０6 〜１５×１０6 の超高分子量ポリオレフィンと（ｂ）重量平均分子量１×１０5 以上１×１０6 未満のポリオレフィンとの組成物７０〜９５％重量％と、（ｃ ' ）低密度ポリエチレンまたは直鎖状低密度ポリエチレン５〜３０重量％とからなり、空孔率が３０〜９５％、平均貫通孔径が０．００１〜１μｍ、引張り破断強度が５００ｋｇ／ｃｍ2 以上であるポリオレフィン微多孔膜に、ポリプロピレン製不織布を積層した電池セパレーター用複合膜に関するものである。
【００１２】
【発明の実施の形態】
本発明の電池セパレーター用複合膜は、ポリオレフィン微多孔膜とポリプロピレン製不織布を積層することによって得られる。以下複合膜について詳細を説明する。
【００１３】
（１）ポリオレフィン微多孔膜
本発明の微多孔膜の空孔率は３０〜９５％、好ましくは３０〜５０％である。空孔率が３０％未満では電解液の空孔内への充填量が少なくなり、好ましくない。一方９５％を超えると膜の機械的強度が小さくなり実用性に劣る。
【００１４】
微多孔膜の平均貫通孔径は０．００１〜１μｍ、好ましくは０．００５〜０．５μｍである。平均貫通孔径が０．００１μｍ未満であると、電解液の空孔内への充填が物理的に困難となるとともに、イオンの通過に支障をきたす。一方１μｍを超える場合は、活物質や反応生成物の拡散を防止することが困難となる。
【００１５】
引張り破断強度は５００ｋｇ／ｃｍ2 以上である。高強度で裂けにくいセパレーターとすることができる。
【００１６】
本発明のポリオレフィン微多孔膜のポリオレフィンは、重量平均分子量が５×１０5 以上、好ましくは１×１０6 〜１５×１０6 のものである。重量平均分子量が５×１０5 未満では、微多孔膜の製造時の延伸工程において最大延伸倍率が低く、目的の微多孔膜が得られない。一方、上限は特に限定的ではないが１５×１０6 を超えるものは、微多孔膜の製造時のゲル状成形物の形成において成形性に劣る。
【００１７】
また、本発明においては、後述のポリオレフィン溶液の高濃度化と微多孔膜の強度の向上を図るために、重量平均分子量１×１０6 〜１５×１０6 の超高分子量ポリオレフィンと重量平均分子量１×１０5 以上１×１０6 未満のポリオレフィンとの組成物を用いることができる。前記超高分子量ポリオレフィン成分のポリオレフィン組成物中の含有量は、ポリオレフィン組成物全体を１００重量％として１重量％以上が好ましく、より好ましくは１０〜７０重量％である。前記超高分子量ポリオレフィンが１重量％未満では、延伸性の向上に寄与する超高分子量ポリオレフィンの分子鎖の絡み合いがほとんど形成されず、高強度の微多孔膜が得られない。
【００１８】
さらに、前記ポリオレフィンまたはそのポリオレフィン組成物の分子量分布の尺度として用いられる重量平均分子量／数平均分子量（以下「Ｍｗ／Ｍｎ」という）は３００以下が好ましく、より好ましくは５〜５０である。このＭｗ／Ｍｎが３００を超えると、延伸時に低分子量成分の破断が起り膜全体の強度が低下するため好ましくない。上記ポリオレフィンとしては、エチレン、プロピレン、１−ブテン、４−メチル−ペンテン−１、１−ヘキセンなどを重合した結晶性の単独重合体、２段重合体、または共重合体及びこれらのブレンド物等が挙げられる。これらのうちではポリプロピレン、ポリエチレン（特に高密度ポリエチレン）及びこれらの組成物等が好ましい。
【００１９】
また、ポリオレフィンまたはポリオレフィン組成物にはポリオレフィン微多孔膜をリチウム電池等のセパレーターとして用い、電極が短絡して電池内部の温度が上昇した時、低温でシャットダウンする機能を付与する物質を加えることができる。
【００２０】
低温シャットダウン性を付与する物質としては、低密度ポリエチレンや低分子量ポリエチレンが挙げられる。低密度ポリエチレンとしては、高圧法の分岐状ポリエチレン（ＬＤＰＥ）及び低圧法による直鎖状の低密度ポリエチレン（ＬＬＤＰＥ）が挙げられる。ＬＤＰＥの場合、その密度は通常０．９ｌ〜０．９３ｇ／ｃｍ3 程度であり、またそのメルトインデックス（ＭＩ １９０℃ ２．１６ｋｇ荷重）は、０．１〜２０ｇ／１０分であるのが好ましく、より好ましくは、０．５〜１０ｇ／１０分である。ＬＬＤＰＥの場合、その密度は通常０．９ｌ〜０．９３ｇ／ｃｍ3 程度であり、またそのメルトインデックス（ＭＩ １９０℃２．１６ｋｇ荷重）は、０．１〜２５ｇ／１０分であるのが好ましく、より好ましくは、０．５〜１０ｇ／１０分である。また、低分子量ポリエチレンとしては重量平均分子量が１０００〜４０００で、融点が８０〜１３０℃の低分子量ポリエチレンである。
【００２１】
前記ＬＤＰＥ、ＬＬＤＰＥ、低分子量ポリエチレン等の配合量は、ポリオレフィンまたはポリオレフィン組成物とＬＤＰＥ、ＬＬＤＰＥもしくは低分子量ポリエチレンの合計を１００重量％として５〜３０重量％、好ましくは５〜２５重量％である。５重量％以下では低温シャットダウン効果が低く、３０重量％以上では得られたポリオレフィン微多孔膜の強度が著しく損なわれる。
【００２２】
本発明のポリオレフィン微多孔膜は、ポリオレフィン、ポリオレフィン組成物またはこれらに低温シャットダウン効果を付与するＬＤＰＥ、ＬＬＤＰＥもしくは、低分子量ポリエチレンを加えた樹脂成分（以下、これらもポリオレフィン組成物という）に有機液状体または固体を混合し、溶融混練後押出成形し、抽出、延伸を施すことにより得られる。また、樹脂成分および有機液状体または固体の混合物に、無機微粉体を添加しても何等差し支えない。本発明のポリオレフィン微多孔膜を得る好ましい方法としては、ポリオレフィン組成物、特に前記ＬＤＰＥ、ＬＬＤＰＥまたは低分子量ポリエチレンを配合したポリオレフィン組成物にポリオレフィンの良溶媒を供給しポリオレフィン組成物の溶液を調製して、この溶液を押出機のダイよりシート状に押し出した後、冷却してゲル状組成物を形成して、このゲル組成物を加熱延伸し、しかる後残存する溶媒を除去する方法である。
【００２３】
本発明において、原料となるポリオレフィンまたはポリオレフィン組成物の溶液は、上述のポリオレフィンまたはポリオレフィン組成物を、溶媒に加熱溶解することにより調製する。この溶媒としては、ポリオレフィンまたはポリオレフィン組成物を十分に溶解できるものであれば特に限定されない。例えば、ノナン、デカン、ウンデカン、ドデカン、流動パラフィンなどの脂肪族または環式の炭化水素、あるいは沸点がこれらに対応する鉱油留分などがあげられるが、溶媒含有量が安定なゲル状成形物を得るためには流動パラフィンのような不揮発性の溶媒が好ましい。加熱溶解は、ポリオレフィンまたはポリオレフィン組成物が完全に溶解する温度で強力に攪拌または押出機で混練しながら行う。その温度は、例えば１４０〜２５０℃の範囲が好ましい。また、ポリオレフィンまたはポリオレフィン組成物の溶液の濃度は、１０〜８０重量％好ましくは１０〜５０重量％である。濃度が１０重量％未満では、使用する溶媒量が多く経済的でないばかりか、シート状に成形する際に、ダイス出口でスウェルやネックインが大きくシートの成形が困難となる。なお、加熱溶解にあたってはポリオレフィンまたはポリオレフィン組成物の酸化を防止するために酸化防止剤を添加するのが好ましい。
【００２４】
次に、このポリオレフィンまたはポリオレフィン組成物の加熱溶液を好ましくはダイスから押し出して成形する。ダイスは、通常長方形の口金形状をしたシートダイスが用いられるが２重円筒状のインフレーションダイスなども用いることができる。シートダイスを用いた場合のダイスギャップは通常０．１〜５ｍｍであり、押し出し成形温度は１４０〜２５０℃である。
【００２５】
このようにしてダイスから押し出された溶液は、冷却することによりゲル状組成物に成形される。冷却方法としては、冷風、冷却水、その他の冷却媒体に直接接触させる方法、冷媒で冷却したロールに接触させる方法などを用いることができる。なお、ダイスから押し出された溶液は、冷却前あるいは冷却中に好ましくは１〜１０、より好ましくは１〜５の引き取り比で引取ってもよい。
【００２６】
次に、このゲル状成形物に延伸を行う。延伸はゲル状成形物を加熱し、通常のテンター法、ロール法、インフレーション法、圧延法もしくはこれらの方法の組み合わせによって所定の倍率で行う。延伸は一軸延伸でも二軸延伸でもよいが、二軸延伸が好ましい。また、二軸延伸の場合は、縦横同時延伸または逐次延伸のいずれでもよい。延伸温度は、ポリオレフィンまたはポリオレフィン組成物の融点＋１０℃以下、好ましくは結晶分散温度から結晶融点未満の範囲である。また延伸倍率は原反の厚さによって異なるが、一軸延伸では２倍以上が好ましく、より好ましくは３〜３０倍である。二軸延伸では面倍率で１０倍以上が好ましく、より好ましくは１５〜４００倍である。面倍率が１０倍未満では延伸が不十分で高弾性、高強度の微多孔膜が得られない。一方、面倍率が４００倍を超えると、延伸操作などで制約が生じる。
【００２７】
得られた延伸成形物は、溶剤で洗浄し残留する溶媒を除去する。洗浄溶剤としては、ペンタン、ヘキサン、ヘプタンなどの炭化水素、塩化メチレン、四塩炭素などの塩素化炭化水素、三フッ化エタンなどのフッ化炭化水素、ジエチルエーテル、ジオキサンなどのエーテル類などの易揮発性のものを用いることができる。これらの溶剤はポリオレフィン組成物の溶解に用いた溶媒に応じて適宜選択し、単独もしくは混合して用いる。洗浄方法は、溶剤に侵漬し抽出する方法、溶剤をシャワーする方法、またはこれらの組合せによる方法などにより行うことができる。
【００２８】
上述のような洗浄は、延伸成形物中の残留溶媒が１重量％未満になるまで行う。その後洗浄溶剤を乾燥するが、洗浄溶剤の乾燥方法は加熱乾燥、風乾などの方法で行うことができる。乾燥した延伸成形物は、結晶分散温度〜融点の温度範囲で熱固定することが望ましい。
【００２９】
以上のようにして製造したポリオレフィン微多孔膜は、空孔率が３０〜９５％で平均貫通孔径が０．００１〜１μｍで、かつ引張り破断強度が５００ｋｇ／ｃｍ2 以上である。またポリオレフィン微多孔膜の厚さは５〜５０μｍである。
【００３０】
（２）ポリプロピレン製不織布
積層体に用いるポリプロピレン製不織布は、繊維径０．１〜５０μｍ、目付け５〜５０ｇ／ｍ2 、好ましくは７〜４５ｇ／ｍ2 、通気度０．１〜１００ｃｃ／ｃｍ2 秒、厚さが４０〜５００μｍのものが好ましい。
【００３１】
（３）積層体
本発明の電池セパレーター用複合膜は上記ポリオレフィン微多孔膜とポリプロピレン製不織布を積層処理することにより得られる。積層処理は通常のカレンダー処理により行う。
【００３２】
積層は、微多孔膜／不織布の２層、不織布／微多孔膜／不織布の３層のように微多孔膜の片側又は両側に不織布を積層してもよい。
【００３３】
積層体の膜厚は、電池用セパレーターとして用いることのできる範囲になるように予熱圧縮ロール及び加熱圧縮ロールをコントロールするのが好ましい。
【００３４】
【実施例】
以下に本発明について実施例を挙げてさらに詳細に説明するが、本発明は実施例に特に限定されるものではない。なお、実施例における試験方法は次の通りである。
（１）膜厚：断面を走査型電子顕微鏡により測定。
（２）空孔率：重量法により測定。
（３）平均貫通孔径：オムニソープ３６０（日機装（株））によって測定。
（４）引張り破断強度：ＡＳＴＭ Ｄ８８２に準拠して測定。
（５）透気度：ＪＩＳ Ｐ８１１７に準拠して測定。
（６）シャットダウン温度：所定温度に加熱することによって、透気度が１０万ｓｅｃ／１００ｃｃ以上となる温度。
（７）メルトダウン温度：所定温度に加熱することによって、膜が溶けて破膜する温度。
【００３５】
実施例１
重量平均分子量が２．５×１０6 の超高分子量ポリエチレン６重量部と重量平均分子量が３．５×１０5 の高密度ポリエチレン２４重量部のポリエチレン組成物１００重量部に酸化防止剤０．３７５重量部を加えたポリエチレン組成物を得た。このポリエチレン組成物３０重量部を二軸押出機（５８ｍｍφ、Ｌ／Ｄ＝４２、強混練タイプ）に投入した。またこの二軸押出機のサイドフィーダーから流動パラフィン７０重量部を供給し、溶融混練して、押出機中にてポリエチレン溶液を調製した。
【００３６】
続いて、この押出機の先端に設置されたＴダイから１９０℃で押し出し、冷却ロールで引取りながらゲル状シートを成形した。続いてこのゲル状シートを、１１５℃で５×５に同時２軸延伸を行い、延伸膜を得た。得られた延伸膜を塩化メチレンで洗浄して残留する流動パラフィンを抽出除去した後、乾燥および熱処理を行い厚さ２５μｍのポリエチレン微多孔膜を得た。
【００３７】
メルトブローポリプロピレン製不織布（繊維径：４μｍ、目付け：７ｇ／ｍ2 、厚さ：６０μｍ）を上記ポリエチレン微多孔膜とカレンダー積層して複合膜を得た。この積層複合膜の物性は表１のようであった。
【００３８】
実施例２
実施例１において、ポリエチレン組成物にＬＤＰＥを５重量部添加し、ポリエチレン微多孔膜の厚さを１５μｍにする以外は実施例１と同様にして複合膜を得た。この積層複合膜の物性は表１のようであった。
【００３９】
実施例３
実施例１において、ポリエチレン組成物に融点が１２６℃、分子量が４０００の低分子量ポリエチレン（ＬＭＷＰＥ）を５重量部添加し、ポリエチレン微多孔膜の厚さを１５μｍにする以外は実施例１と同様にして複合膜を得た。この積層複合膜の物性は表１のようであった。
【００４０】
実施例４
実施例１において、ポリエチレン組成物に融点が１１６℃、分子量が１０００の低分子量ポリエチレン（ＬＭＷＰＥ）を５重量部添加し、ポリエチレン微多孔膜の厚さを１５μｍにする以外は実施例１と同様にして複合膜を得た。この積層複合膜の物性は表１のようであった。
【００４１】
実施例５
実施例１の積層において、ポリプロピレン製不織布をポリエチレン微多孔膜の両側に積層して３層体にする以外は実施例１と同様にして複合膜を得た。この積層複合膜の物性は表１のようであった。
【００４２】
実施例６
実施例１のポリプロピレン製不織布として、繊維径：４μｍ、目付け：４０ｇ／ｍ2 、厚さ：４４０μｍを用いる以外は実施例１と同様にして複合膜を得た。この積層複合膜の物性は表１のようであった。
【００４３】
実施例７
実施例１のポリプロピレン製不織布として、繊維径：４μｍ、目付け：２２ｇ／ｍ2 、厚さ：２３０μｍを用いる以外は実施例１と同様にして複合膜を得た。この積層複合膜の物性は表１のようであった。
【００４４】
比較例１
実施例１において得られたポリエチレン微多孔膜の物性は表１のようであった。
【００４５】
【表１】
【００４６】
【発明の効果】
本発明のポリオレフィン微多孔膜とポリプロピレン不織布の積層複合膜を電池セパレーターとして用いた場合、異常時に温度が上昇した際には、ポリオレフィン微多孔膜の方がまず、より低温において軟化、溶融してその孔部を閉塞することにより、短絡電流を減少させるとともに、ポリプロピレン不織布は多孔性支持体として作用し、短絡電流を減少させる機能を高温まで維持しつつ、かつ、高温まで正負電極間の短絡を防止することができ、リチウム電池用セパレーターとして用いる場合は、安全性の点でおおいに信頼できる。[0001]
BACKGROUND OF THE INVENTION
The present invention is used as a separator corresponding to a non-aqueous solvent battery such as a lithium battery, has excellent permeation performance and mechanical strength, has a function of blocking permeability at a low temperature during abnormal heat generation due to a short circuit, and The present invention relates to a highly safe composite membrane for battery separators.
[0002]
[Prior art]
Polyolefin microporous membranes are used in various separation membranes, battery separators, electrolytic capacitor separators, and the like. Particularly in lithium batteries, since a lithium metal and lithium ions are used, an aprotic polar organic solvent is used as an electrolyte solvent, and a lithium salt is used as an electrolyte. Therefore, the separator installed between the positive electrode and the negative electrode is made by processing a polyolefin-based material such as polyethylene or polypropylene that is insoluble in an organic solvent and stable to an electrolyte or an electrode active material into a microporous film or a nonwoven fabric. Used as a separator.
[0003]
Recently, high-strength and high-elasticity microporous membranes have been developed using ultra-high molecular weight polyolefins. For example, a gel-like sheet is formed from a solution obtained by heating and dissolving an ultra-high molecular weight polyolefin having a weight average molecular weight of 7 × 10 5 or more in a solvent, and the solvent amount in the gel-like sheet is adjusted by a desolvation treatment, and then heated There has been proposed a method for producing a microporous membrane by removing the residual solvent after stretching (Japanese Patent Laid-Open No. 60-242035). Further, as a method for producing a polyolefin microporous membrane from a high-concentration solution of ultra-high molecular weight polyolefin, there has been proposed a method in which the molecular weight distribution of a polyolefin composition containing ultra-high molecular weight polyolefin is set to a specific value (Japanese Patent Laid-open No. Hei 3- 64334).
[0004]
By the way, when the polyolefin microporous membrane is used for a lithium battery separator or the like, it is necessary to prevent an accident such as ignition when the electrode is short-circuited and the temperature inside the battery is increased. For this reason, it is necessary for the separator to have a function of melting and clogging the hole before lithium ignition and shutting down the current. However, in each of the above-mentioned microporous membranes, the permeability cutoff temperature due to the blockage of the microporous membrane is not necessarily sufficiently low in terms of safety, and in order to further improve safety, the current is shut down at a lower temperature. It is desirable to use a separator that causes Therefore, it is considered that the lower the non-porous temperature and the larger the difference between the non-porous temperature and the film breaking temperature, the better the high temperature characteristics and the higher the safety of the battery separator.
[0005]
As a technique for providing a shutdown function when a battery separator is short-circuited, Japanese Patent Application Laid-Open No. 60-23594 discloses that when a battery is short-circuited externally, the temperature inside the battery rises due to Joule heat and the separator member melts. It is disclosed that it is desirable to use a single-layer microporous film made of polypropylene or polyethylene for the purpose of preventing accidents such as ignition and explosion of the battery by short-circuiting.
[0006]
In batteries using polypropylene and polyethylene microporous films, when the external short circuit occurs, the battery temperature rises due to Joule heat, and when the melting point of each film material is reached, the micropores are blocked by the melt. Since the insulator is an insulator that prevents ion migration as well as static insulation, no current flows. As a result, it is described that the inconvenience such as ignition and explosion is suppressed without increasing the battery temperature further. However, in the above non-aqueous electrolyte separator, although the safety is improved to some extent, the temperature rises, and the cohesive force of the resin becomes small near the melting point of the thermoplastic resin, and the separator may be broken. It is not enough to solve the danger of fire, explosion.
[0007]
[Problems to be solved by the invention]
Therefore, the subject of this invention is providing the composite film for battery separators which was excellent in the permeation | transmission performance and mechanical strength, and was excellent in the safety | security which has the function to interrupt | block permeability at low temperature.
[0008]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention is excellent in permeation performance and mechanical strength by laminating a microporous membrane made of a composition containing an ultrahigh molecular weight polyolefin or a component thereof and a nonwoven fabric made of polypropylene, and at a low temperature. The inventors have found that a composite membrane that blocks permeability and is excellent in safety can be obtained, and have arrived at the present invention.
[0009]
That is, the first of the present invention is a polyolefin having a weight average molecular weight of 5 × 10 5 or more or a weight average molecular weight of 5 × 10 5. A polyolefin microporous membrane comprising a polyolefin composition containing the above ultrahigh molecular weight polyolefin , having a porosity of 30 to 95%, an average through-hole diameter of 0.001 to 1 μm, and a tensile breaking strength of 500 kg / cm 2 or more. The present invention relates to a composite membrane for a battery separator in which a polypropylene nonwoven fabric is laminated.
[0010]
In the second aspect of the present invention, a polyolefin composition containing a polyolefin having a weight average molecular weight of 5 × 10 5 or more is: (a) an ultrahigh molecular weight polyolefin having a weight average molecular weight of 1 × 10 6 to 15 × 10 6 or (a ) with a composition 70-95 wt% of the weight-average molecular weight 1 × 10 6 to 15 × 10 6 ultra high molecular weight polyolefin and (b) a weight-average molecular weight 1 × 10 5 to 1 × 10 of less than 6 polyolefins, (c ) a weight average molecular weight of 1000 to 4000, a melting point consists of a low molecular weight polyethylene 5-30 wt% of 80 to 130 ° C., porosity 30 to 95%, an average through-pore diameter of 0.001 to, tensile rupture The present invention relates to a composite membrane for battery separator in which a polypropylene non-woven fabric is laminated on a polyolefin microporous membrane having a strength of 500 kg / cm 2 or more.
[0011]
Further, according to a third aspect of the present invention, a polyolefin composition containing a polyolefin having a weight average molecular weight of 5 × 10 5 or more is: (a) an ultrahigh molecular weight polyolefin having a weight average molecular weight of 1 × 10 6 to 15 × 10 6 or (a ) and the composition 70% to 95% by weight percent of the weight-average molecular weight 1 × 10 6 to 15 × 10 6 ultra high molecular weight polyolefin and (b) a weight-average molecular weight 1 × 10 5 to 1 × 10 of less than 6 polyolefin, ( c ') consists of a low density polyethylene or linear low density polyethylene 5 to 30 wt%, the porosity 30 to 95%, an average through-pore diameter of 0.001 to, tensile strength at break 500 kg / cm 2 or more The present invention relates to a composite membrane for a battery separator in which a polypropylene non-woven fabric is laminated on a polyolefin microporous membrane.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The composite membrane for battery separator of the present invention is obtained by laminating a polyolefin microporous membrane and a polypropylene nonwoven fabric. Details of the composite membrane will be described below.
[0013]
(1) Polyolefin microporous membrane The porosity of the microporous membrane of the present invention is 30 to 95%, preferably 30 to 50%. If the porosity is less than 30%, the amount of electrolyte filled in the pores decreases, which is not preferable. On the other hand, if it exceeds 95%, the mechanical strength of the film becomes small and the practicality is inferior.
[0014]
The average through-hole diameter of the microporous membrane is 0.001-1 μm, preferably 0.005-0.5 μm. When the average through-hole diameter is less than 0.001 μm, it becomes physically difficult to fill the pores of the electrolytic solution, and the passage of ions is hindered. On the other hand, when it exceeds 1 μm, it becomes difficult to prevent the diffusion of the active material and the reaction product.
[0015]
The tensile strength at break is 500 kg / cm 2 or more. It can be a high strength and difficult to tear separator.
[0016]
The polyolefin of the polyolefin microporous membrane of the present invention has a weight average molecular weight of 5 × 10 5 or more, preferably 1 × 10 6 to 15 × 10 6 . When the weight average molecular weight is less than 5 × 10 5 , the maximum stretching ratio is low in the stretching step during the production of the microporous membrane, and the target microporous membrane cannot be obtained. On the other hand, although the upper limit is not particularly limited, those exceeding 15 × 10 6 are inferior in moldability in the formation of a gel-like molded product during production of the microporous membrane.
[0017]
In the present invention, an ultrahigh molecular weight polyolefin having a weight average molecular weight of 1 × 10 6 to 15 × 10 6 and a weight average molecular weight of 1 are used to increase the concentration of the polyolefin solution described later and improve the strength of the microporous membrane. A composition with a polyolefin of × 10 5 or more and less than 1 × 10 6 can be used. The content of the ultrahigh molecular weight polyolefin component in the polyolefin composition is preferably 1% by weight or more, more preferably 10 to 70% by weight, based on 100% by weight of the entire polyolefin composition. When the amount of the ultrahigh molecular weight polyolefin is less than 1% by weight, entanglement of molecular chains of the ultrahigh molecular weight polyolefin contributing to the improvement of stretchability is hardly formed, and a high-strength microporous film cannot be obtained.
[0018]
Furthermore, the weight average molecular weight / number average molecular weight (hereinafter referred to as “Mw / Mn”) used as a measure of the molecular weight distribution of the polyolefin or its polyolefin composition is preferably 300 or less, more preferably 5 to 50. When Mw / Mn exceeds 300, the low molecular weight component breaks during stretching and the strength of the entire film is lowered, which is not preferable. Examples of the polyolefin include a crystalline homopolymer, a two-stage polymer, a copolymer and a blend thereof obtained by polymerizing ethylene, propylene, 1-butene, 4-methyl-pentene-1, 1-hexene, and the like. Is mentioned. Of these, polypropylene, polyethylene (particularly high-density polyethylene) and compositions thereof are preferred.
[0019]
In addition, a polyolefin microporous membrane can be used as a separator for a lithium battery or the like in a polyolefin or a polyolefin composition, and a substance that gives a function of shutting down at a low temperature when an electrode is short-circuited and the temperature inside the battery rises can be added. .
[0020]
Examples of the substance that imparts a low temperature shutdown property include low density polyethylene and low molecular weight polyethylene. Examples of the low density polyethylene include high-pressure branched polyethylene (LDPE) and low-pressure linear low-density polyethylene (LLDPE). In the case of LDPE, the density is usually about 0.9 l to 0.93 g / cm 3 , and the melt index (MI 190 ° C. 2.16 kg load) is preferably 0.1 to 20 g / 10 min. More preferably, it is 0.5 to 10 g / 10 min. In the case of LLDPE, the density is usually about 0.9 l to 0.93 g / cm 3 , and the melt index (MI 190 ° C. 2.16 kg load) is preferably 0.1 to 25 g / 10 min. More preferably, it is 0.5 to 10 g / 10 min. The low molecular weight polyethylene is a low molecular weight polyethylene having a weight average molecular weight of 1000 to 4000 and a melting point of 80 to 130 ° C.
[0021]
The blending amount of the LDPE, LLDPE, low molecular weight polyethylene or the like is 5 to 30% by weight, preferably 5 to 25% by weight, where the total of the polyolefin or polyolefin composition and LDPE, LLDPE or low molecular weight polyethylene is 100% by weight. If it is 5% by weight or less, the low-temperature shutdown effect is low, and if it is 30% by weight or more, the strength of the polyolefin microporous film obtained is significantly impaired.
[0022]
The polyolefin microporous membrane of the present invention is an organic liquid substance in a polyolefin, a polyolefin composition, or a resin component obtained by adding LDPE, LLDPE, or low molecular weight polyethylene that imparts a low-temperature shutdown effect thereto (hereinafter also referred to as a polyolefin composition). Or it is obtained by mixing solid, melt-kneading, extruding, extracting and stretching. Further, it is possible to add inorganic fine powder to the resin component and the organic liquid or solid mixture. A preferred method for obtaining the polyolefin microporous membrane of the present invention is to prepare a polyolefin composition solution by supplying a polyolefin good solvent to a polyolefin composition, especially a polyolefin composition containing the LDPE, LLDPE or low molecular weight polyethylene. This solution is a method of extruding this solution into a sheet form from a die of an extruder, cooling to form a gel composition, heating and stretching the gel composition, and then removing the remaining solvent.
[0023]
In the present invention, the polyolefin or polyolefin composition solution used as a raw material is prepared by dissolving the above-described polyolefin or polyolefin composition in a solvent by heating. The solvent is not particularly limited as long as it can sufficiently dissolve the polyolefin or the polyolefin composition. For example, aliphatic or cyclic hydrocarbons such as nonane, decane, undecane, dodecane, liquid paraffin, or mineral oil fractions with boiling points corresponding to these, but gel-like molded products with a stable solvent content can be used. Nonvolatile solvents such as liquid paraffin are preferred for obtaining. The dissolution by heating is performed while vigorously stirring or kneading with an extruder at a temperature at which the polyolefin or polyolefin composition is completely dissolved. The temperature is preferably in the range of 140 to 250 ° C, for example. The concentration of the polyolefin or polyolefin composition solution is 10 to 80% by weight, preferably 10 to 50% by weight. If the concentration is less than 10% by weight, the amount of solvent used is large and not economical, and when forming into a sheet, swell and neck-in are large at the die outlet, making it difficult to form the sheet. In addition, it is preferable to add an antioxidant in order to prevent the polyolefin or the polyolefin composition from being oxidized at the time of heating and dissolving.
[0024]
Next, the heated solution of the polyolefin or polyolefin composition is preferably extruded from a die. As the die, a sheet die having a rectangular base shape is usually used, but a double cylindrical inflation die can also be used. When a sheet die is used, the die gap is usually 0.1 to 5 mm, and the extrusion molding temperature is 140 to 250 ° C.
[0025]
The solution thus extruded from the die is formed into a gel composition by cooling. As a cooling method, a method of directly contacting cold air, cooling water, or another cooling medium, a method of contacting a roll cooled by a refrigerant, or the like can be used. The solution pushed out from the die may be taken up at a take-up ratio of preferably 1 to 10, more preferably 1 to 5 before or during cooling.
[0026]
Next, the gel-like molded product is stretched. Stretching is performed at a predetermined magnification by heating the gel-like molded article and using a normal tenter method, roll method, inflation method, rolling method, or a combination of these methods. The stretching may be uniaxial stretching or biaxial stretching, but biaxial stretching is preferred. In the case of biaxial stretching, either longitudinal or transverse simultaneous stretching or sequential stretching may be used. The stretching temperature is the melting point of the polyolefin or polyolefin composition + 10 ° C. or less, preferably in the range from the crystal dispersion temperature to less than the crystal melting point. Moreover, although a draw ratio changes with thickness of an original fabric, in uniaxial stretching, 2 times or more are preferable, More preferably, it is 3 to 30 times. In biaxial stretching, the surface magnification is preferably 10 times or more, more preferably 15 to 400 times. If the surface magnification is less than 10 times, stretching is insufficient and a highly elastic, high-strength microporous film cannot be obtained. On the other hand, when the surface magnification exceeds 400 times, a restriction occurs in a stretching operation or the like.
[0027]
The obtained stretched molded product is washed with a solvent to remove the remaining solvent. Cleaning solvents include hydrocarbons such as pentane, hexane and heptane, chlorinated hydrocarbons such as methylene chloride and tetrasalt carbon, fluorinated hydrocarbons such as ethane trifluoride, and ethers such as diethyl ether and dioxane. Volatile ones can be used. These solvents are appropriately selected according to the solvent used for dissolving the polyolefin composition, and used alone or in combination. The washing method can be performed by a method of immersing and extracting in a solvent, a method of showering a solvent, or a method of a combination thereof.
[0028]
Washing as described above is performed until the residual solvent in the stretched molded product is less than 1% by weight. Thereafter, the cleaning solvent is dried. The cleaning solvent can be dried by heat drying, air drying, or the like. The dried stretched molded product is preferably heat-set within the temperature range of the crystal dispersion temperature to the melting point.
[0029]
The polyolefin microporous membrane produced as described above has a porosity of 30 to 95%, an average through-hole diameter of 0.001 to 1 μm, and a tensile breaking strength of 500 kg / cm 2 or more. The polyolefin microporous membrane has a thickness of 5 to 50 μm.
[0030]
(2) The polypropylene nonwoven fabric used for the polypropylene nonwoven fabric laminate has a fiber diameter of 0.1 to 50 μm, a basis weight of 5 to 50 g / m 2 , preferably 7 to 45 g / m 2 , and an air permeability of 0.1 to 100 cc / cm 2. Those having a thickness of 40 to 500 μm are preferable.
[0031]
(3) Laminate The composite membrane for battery separator of the present invention can be obtained by laminating the polyolefin microporous membrane and a polypropylene nonwoven fabric. The lamination process is performed by a normal calendar process.
[0032]
Lamination may be performed by laminating the nonwoven fabric on one side or both sides of the microporous membrane, such as two layers of microporous membrane / nonwoven fabric and three layers of nonwoven fabric / microporous membrane / nonwoven fabric.
[0033]
It is preferable to control the preheating compression roll and the heating compression roll so that the film thickness of the laminate is in a range that can be used as a battery separator.
[0034]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not particularly limited to the examples. In addition, the test method in an Example is as follows.
(1) Film thickness: The cross section was measured with a scanning electron microscope.
(2) Porosity: measured by gravimetric method.
(3) Average through-hole diameter: Measured with Omni Soap 360 (Nikkiso Co., Ltd.).
(4) Tensile strength at break: Measured according to ASTM D882.
(5) Air permeability: Measured according to JIS P8117.
(6) Shutdown temperature: A temperature at which the air permeability becomes 100,000 sec / 100 cc or more by heating to a predetermined temperature.
(7) Meltdown temperature: The temperature at which a film melts and breaks when heated to a predetermined temperature.
[0035]
Example 1
An antioxidant 0.375 is added to 100 parts by weight of a polyethylene composition of 6 parts by weight of ultrahigh molecular weight polyethylene having a weight average molecular weight of 2.5 × 10 6 and 24 parts by weight of high density polyethylene having a weight average molecular weight of 3.5 × 10 5. A polyethylene composition added with parts by weight was obtained. 30 parts by weight of this polyethylene composition was put into a twin screw extruder (58 mmφ, L / D = 42, strong kneading type). Further, 70 parts by weight of liquid paraffin was supplied from the side feeder of this twin screw extruder, melt kneaded, and a polyethylene solution was prepared in the extruder.
[0036]
Subsequently, a gel-like sheet was formed while being extruded at 190 ° C. from a T die installed at the tip of the extruder and being taken up by a cooling roll. Subsequently, this gel-like sheet was subjected to simultaneous biaxial stretching at 115 ° C. in 5 × 5 to obtain a stretched film. The obtained stretched membrane was washed with methylene chloride to extract and remove the remaining liquid paraffin, followed by drying and heat treatment to obtain a polyethylene microporous membrane having a thickness of 25 μm.
[0037]
A nonwoven fabric made of melt blown polypropylene (fiber diameter: 4 μm, basis weight: 7 g / m 2 , thickness: 60 μm) was calendered on the polyethylene microporous membrane to obtain a composite membrane. Table 1 shows the physical properties of this laminated composite film.
[0038]
Example 2
In Example 1, a composite membrane was obtained in the same manner as in Example 1 except that 5 parts by weight of LDPE was added to the polyethylene composition and the thickness of the polyethylene microporous membrane was changed to 15 μm. Table 1 shows the physical properties of this laminated composite film.
[0039]
Example 3
In Example 1, 5 parts by weight of a low molecular weight polyethylene (LMWPE) having a melting point of 126 ° C. and a molecular weight of 4000 was added to the polyethylene composition, and the thickness of the polyethylene microporous film was changed to 15 μm. Thus, a composite membrane was obtained. Table 1 shows the physical properties of this laminated composite film.
[0040]
Example 4
In Example 1, 5 parts by weight of low molecular weight polyethylene (LMWPE) having a melting point of 116 ° C. and a molecular weight of 1000 was added to the polyethylene composition, and the thickness of the polyethylene microporous film was changed to 15 μm. Thus, a composite membrane was obtained. Table 1 shows the physical properties of this laminated composite film.
[0041]
Example 5
In the lamination of Example 1, a composite membrane was obtained in the same manner as in Example 1 except that a polypropylene nonwoven fabric was laminated on both sides of the polyethylene microporous membrane to form a three-layer body. Table 1 shows the physical properties of this laminated composite film.
[0042]
Example 6
As the polypropylene nonwoven fabric of Example 1, a composite membrane was obtained in the same manner as in Example 1 except that fiber diameter: 4 μm, basis weight: 40 g / m 2 , and thickness: 440 μm were used. Table 1 shows the physical properties of this laminated composite film.
[0043]
Example 7
As the polypropylene nonwoven fabric of Example 1, a composite membrane was obtained in the same manner as in Example 1 except that the fiber diameter was 4 μm, the basis weight was 22 g / m 2 , and the thickness was 230 μm. Table 1 shows the physical properties of this laminated composite film.
[0044]
Comparative Example 1
Table 1 shows the physical properties of the polyethylene microporous membrane obtained in Example 1.
[0045]
[Table 1]
[0046]
【The invention's effect】
When the laminated composite membrane of the polyolefin microporous membrane and the polypropylene nonwoven fabric of the present invention is used as a battery separator, when the temperature rises at the time of abnormality, the polyolefin microporous membrane is first softened and melted at a lower temperature. By closing the hole, the short-circuit current is reduced, and the polypropylene nonwoven fabric acts as a porous support, maintaining the function of reducing the short-circuit current up to a high temperature and preventing a short circuit between the positive and negative electrodes up to a high temperature. When used as a lithium battery separator, it is very reliable in terms of safety.
Claims (6)
Priority Applications (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16377696A JP3682120B2 (en) | 1996-06-04 | 1996-06-04 | Composite membrane for battery separator and battery separator |
| US08/864,079 US5922492A (en) | 1996-06-04 | 1997-05-28 | Microporous polyolefin battery separator |
| EP97303786A EP0811479B1 (en) | 1996-06-04 | 1997-06-03 | Microporous polyolefin composition membrane, production method thereof and battery separator |
| CA002206940A CA2206940C (en) | 1996-06-04 | 1997-06-03 | Microporous polyolefin composition membrane, production method thereof and battery separator |
| DE69724513T DE69724513T2 (en) | 1996-06-04 | 1997-06-03 | Microporous membrane of a polyolefin composition, process for its production and battery separator |
| KR1019970022997A KR100452784B1 (en) | 1996-06-04 | 1997-06-04 | Microporous Polyolefin Composite Membrane, Manufacturing Method Thereof and Battery Separator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16377696A JP3682120B2 (en) | 1996-06-04 | 1996-06-04 | Composite membrane for battery separator and battery separator |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09326250A JPH09326250A (en) | 1997-12-16 |
| JP3682120B2 true JP3682120B2 (en) | 2005-08-10 |
Family
ID=15780510
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16377696A Expired - Fee Related JP3682120B2 (en) | 1996-06-04 | 1996-06-04 | Composite membrane for battery separator and battery separator |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3682120B2 (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100558840B1 (en) * | 1998-09-24 | 2006-07-03 | 에스케이씨 주식회사 | Microporous separator and its manufacturing method |
| JP2000108249A (en) * | 1998-10-08 | 2000-04-18 | Tonen Chem Corp | Laminated composite film |
| KR100373204B1 (en) * | 2000-08-12 | 2003-02-25 | 주식회사 엘지화학 | Multi-component composite membrane for polymer electrolyte and method of preparing the same |
| KR100406689B1 (en) * | 2001-03-05 | 2003-11-21 | 주식회사 엘지화학 | Multicomponent composite film for electrochemical device and method for preparing the same |
| JP5057414B2 (en) * | 2004-01-21 | 2012-10-24 | 東レバッテリーセパレータフィルム株式会社 | Method for producing microporous membrane and use of microporous membrane obtained by the production method |
| KR20060001849A (en) * | 2005-11-15 | 2006-01-06 | (주)인터포어 | Film for packaging of fresh or fermentation food and container |
| JP5629542B2 (en) * | 2010-10-04 | 2014-11-19 | 旭化成イーマテリアルズ株式会社 | Polyolefin microporous membrane |
| JP5942134B2 (en) * | 2013-02-04 | 2016-06-29 | 旭化成株式会社 | Polyolefin microporous membrane |
| KR102544227B1 (en) * | 2016-04-12 | 2023-06-16 | 에스케이이노베이션 주식회사 | Separator for lithium secondary battery and lithium secondary battery containing thereof |
| JP6443696B2 (en) * | 2016-09-27 | 2018-12-26 | トヨタ自動車株式会社 | Secondary battery |
| CN113809473B (en) * | 2018-07-19 | 2023-04-07 | 河南天工膜材新能源科技有限公司 | Polypropylene diaphragm and preparation method thereof |
| DE102019112089A1 (en) * | 2019-05-09 | 2020-11-12 | Brückner Maschinenbau GmbH & Co. KG | Film with at least two layers and method for their manufacture |
| CN112909428B (en) * | 2021-01-26 | 2023-04-21 | 南京捷纳思新材料有限公司 | Battery diaphragm and preparation method thereof |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60242035A (en) * | 1984-04-27 | 1985-12-02 | Toa Nenryo Kogyo Kk | Microporous polyethylene film and production thereof |
| JPS61263043A (en) * | 1985-05-17 | 1986-11-21 | Matsushita Electric Ind Co Ltd | Organic electrolyte battery |
| JP2882675B2 (en) * | 1990-10-29 | 1999-04-12 | 株式会社クラレ | Separator sheet |
| JP2657434B2 (en) * | 1991-07-19 | 1997-09-24 | 東燃株式会社 | Polyethylene microporous membrane, method for producing the same, and battery separator using the same |
| JP3072163B2 (en) * | 1991-10-03 | 2000-07-31 | 東燃株式会社 | Polyolefin microporous membrane, method for producing the same, and battery separator using the same |
| JP3080731B2 (en) * | 1991-10-17 | 2000-08-28 | 富士電気化学株式会社 | Method of manufacturing coin-shaped lithium secondary battery |
| JPH0722014A (en) * | 1993-07-06 | 1995-01-24 | Mitsubishi Chem Corp | Separator for battery |
| JPH0773863A (en) * | 1993-08-31 | 1995-03-17 | Kanai Hiroyuki | Separator for alkaline battery |
| JPH0820659A (en) * | 1994-07-08 | 1996-01-23 | Daicel Chem Ind Ltd | Microporous membrane, its production and separator for non-aqueous electrolyte solution cell |
-
1996
- 1996-06-04 JP JP16377696A patent/JP3682120B2/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| JPH09326250A (en) | 1997-12-16 |
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